Hello, I have just finished putting a thermo fan on my radiator and I’m having trouble getting the wiring to work. Well I can make the fan work with a manual switch but not with a thermo switch

I have got a thermostat housing that has a provision for a thermo switch (as shown below), however the thermo switch has only one terminal on it and I don't know how to wire up a single terminal switch, when i connect all the wires up as the diagram says to and turn the ignition on. It turns the fan on at the same time. Regardless of water temperature. This shouldn't be happening, the way the thermo switch seems to be working at the moment is not like a switch at all, its acting as like a constant earth.

Does anyone know how to wire this up correctly so that the switch works when it is supposed to (when it gets hot)

I did have to bend the terminal a little to get it to fit though, and I changed the rubber washer it had on it for a fiber one (no that it should make any difference)

Have I wired it up wrong, got a faulty switch or damaged the switch?

Any help would be much appreciated

This is how the diagram says to wire up a thermo switch (I think it’s referring to a 2 wire switch)


This is how I have connected the single teminal thermo switch

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1275 + weber = fun

Have you tried swapping the connection to the fan motor from
terminal 87a to 87

This will help if you have a problem with NO / NC with either the switch or the relay.

Worth a try?

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Too many cars, and too little time.

yeah i have tried a new relay and i tried swaping the fan connections from 87 to 87a. still no joy, the fan still comes on when the ignition is on

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1275 + weber = fun

Looks good to me - I'd take the thermo switch out and start testing with a test light/meter. If it's got a complete circuit between the terminal and the thread when it's cold then I'd say it's a bad switch.

Mine was doing the opposite - not closing until way too hot. Ended up bypassing it and putting in a manual switch.

Hang on, that can't be right

If the thermo switch was faulty & you changed the fan motor from 87 (normally open)
to 87a (normally closed), then the fan should never run!

You must have messed up your connections & are suppling power directly from the ignition switch to the fan motor.

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Too many cars, and too little time.

I ended up buying a temperature switch kit from Jaycar.It allows you to adjust the temperature settings to suit.
I got an old temperature switch and pulled the guts of it out and epoxied the temperature sensor from the kit into it and then mounted it like you have into the thermostat housing.
So far it seems to work reasonably well and with a bit of fiddling with another relay its operating as a two stage setup, half speed at startup and full speed at the trigger point.

Im confused now, in the diagram, there is constant power to the ignition switch,

now as i understand it, the theory is that when you turn the car on there is power going from the ignition switch to the termo switch, so that when the thermo switch heats up to the right temperature it "earths" therby completing the circuit and tuning the fan on,

however it seems like the swtich isn't "switching", its staying on, this says to me that either the switch is faulty, or that the switch works in reverse and is always on... until it reaches the designated temperature and then switches off.

is this possible? it seems pretty wierd to me

I found this tread on the toymods site... I have a TFS136 swtich but there are heaps of other thermo switches which only have 1 terminal, there has to be a way to make it work. has anyone used a single terminal thermo swtich

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1275 + weber = fun

You seem to have gotten yourself all confused.

Here is a simple way to rule out the thermo switch as the problem:
1. with everything on, remove the wire to the switch on the thermostat housing.
2. touch this wire directly to the thermostat housing

If this makes no difference (i.e. the fan doesn't go on & off as you earth out that wire)
then there is a problem with how you wired the relay & it's nothing to do with the thermo switch

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Too many cars, and too little time.

Mate I'm pretty sure its not a thermatic switch you've got there but a water temperature gauge sender. The early a-series engines had them housed in the head but the later cars had a provision for one in the thermostat housing (just like the one you have).

A thermatic switch is just that - a switch - it has two terminals and is normaly an open ciruit - once the temperature reaches a certain level the switch closes the circuit between the two terminals. In a car equiped with a thermo fan this would ativate the fan's relay which would in turn cause the fan to work until the temperature falls enough to open the switch's circuit again. Some of them come with an adjustment of the activation temperature but some dont.

There's no way this can happen when the switch only has a single terminal - which is usualy the sender unit for a temp guage which only needs one terminal as it picksup variations in the resistance inside the switch due to temperature (I believe).

Yea a switch could be grounded via the block without the need for an extra terminal but I dont reckon the cast alloy housing would be such a good conductor

Now some cars had simple two terminal switches instaled (which would look just like yours but with two terminals) I have a couple from the wreckers. You can try your luck there - a screw in probe having two terminals and being piped in close to the radiator would be a dead giveaway).

You can test them by making sure there's an open circuit b/w the terminals when cold and then heat it up in a pot of water on the stowe. You should hear a click just before the water starts to boil and the switch will now have conact between the terminals until it cools again.

Cheers

Ok, so i have everything wired up as the diagram shows and i turned the ignition on...this made the fan come on....so then i disconnected the terminal on the termo switch and the fan stopped...i then touched the terminal onto the thermostat housing...and the fan came on again...what does that mean?

also, sorry i forgot to add the link to the thread in my last post here it is
http://www.toymods.net/forums/showthread.php?t=5125

the part number I said i had was TFS136 (Thermatic Fan Switch 136) and on the box for for the switch it said clealy that it was a thermatic fan swtich, and i also have a switch almost exactly like this one on my mazda, its only got one teminal aswell, so there has to be a way to make it work, but its getting to be a bit too hard now, ill think ill just have to see if i can fin a 2 terminal one that will fit

thanks heaps for your help boys

cheers

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1275 + weber = fun

Have you actually tried the tests stated above? eg is there a complete circuit between the thread and the terminal when the unit is cold?

OK Benny_boy, you have proven that the thermo switch is either:
a. stuffed or
b. normally closed

If you change the terminal you have the fan connected to from 87 to 87a,
then the fan will either:
a. not work at all (switch stuffed) or
b. work when engine is hot enough (switch operating as NC)

Hope that helps...

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Too many cars, and too little time.

I have tried absolutetly everything, As i said my mazda has a similar switch too (only 1 terminal), so i wired my mini up with exactly the same circuit as the mazda and even that still didn't make it work properly, so my only conclusion is that the switch is faulty. I'm gonna try and get another switch tomorrow and try it. I think ill try one with 2 teminals this time.

thanks for the help guys. i'll keep you posted on the results

cheers

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1275 + weber = fun

Ok I was wrong then - it might be a thermatic switch after all - if you wire the fan up as per diagram you need the switch to close the circuit b/w its thread that touches the thermostat housing (which is grounded to the engine) and the terminal. Now as touching the terminal directly to the housing makes the fan works it means that if the switch worked correctly the system should have worked fine.

Now check that there is no continuity b/w the terminal on the switch and the thread on the switch. then heat up the switch untill the water almoust starts boiling and it should click and there should be continuity b/w the terminal and the thread - otherwise the switch is stuffed -> go to the wreckers where you can take stuff off the cars yourself (";pick and payless" in syd. dunno about Melbourne) and get a two terminal switch with the correct thread size off a car.

Cheers

I finally got it working, yay.

I changed the thermo switch to a 2 terminal tridon open circuit switch and it worked. i had to modify the switch and grind a little bit of the rocker cover to make everything fit nicely tho.

I've been running it for about a month now and its sweet as, love this mod so much. no more cappy shroud, no more mech fan. in the cold weather the theomo fan rarely even needs to turn on, and in the hotter weather it keeps the engine temp right where it should be.

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1275 + weber = fun